Frame structure for multi-hop relay in wireless communication systems

ABSTRACT

Implementations of systems and techniques for scheduling wireless transmission of data blocks between a base station (BS) and one or more relay stations (RSs) in a wireless relay communication network.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/858,118, filed Sep. 19, 2007, which claims the benefit ofU.S. Provisional Patent Application No. 60/845,950, filed Sep. 19, 2006.The entire contents of the before-mentioned patent applications areincorporated by reference as part of the disclosure of this application.

BACKGROUND

This application relates to wireless communication systems andtechniques for wireless communications using one or more relay stationsin addition to base stations.

Wireless communication systems use electromagnetic waves to communicatewith fixed and mobile wireless communication devices, e.g., mobilewireless phones and laptop computers with wireless communication cards,that are located within cells of coverage areas of the systems. A radiospectral range or band designated or allocated for a wirelesscommunication service or a particular class of wireless services may bedivided into different radio carrier frequencies for generatingdifferent communication frequency channels. Such systems use basestations spatially distributed to provide radio coverage in a geographicservice area which is divided into cells. In such a cellular deployment,each base station (BS) is conceptually located at the center of arespective cell to provide radio coverage for that cell and transmitsinformation to a wireless subscriber station (SS) such as a mobile SS(MSS) via BS-generated downlink (DL) radio signals. A subscriber stationat a particular cell transmits information to its serving base stationfor that particular cell via uplink (UL) radio signals. The basestations can include directional antennas to further divide each cellinto different cell sectors where each antenna covers one sector. Thissectorization of a cell increases the communication capacity.

The radio coverage of a network of fixed base stations may be limiteddue to various factors. Various structures may block the radio signalsof certain base stations. For example, a tall building may shield aparticular area from the radio signal from a base station, thus creatinga undesired shadowing. At the edge of a radio cell, the signal strengthcan be weak and hence can increase the error rate in the wirelesscommunications. One approach to mitigating these and other limitationsis to increase the number of base stations in a given service area. Inone implementation under this approach, one or more relay stations (RSs)can be deployed among certain fixed base stations to relay communicationsignals between a subscriber station and a base station, thus extendingthe coverage and improving the communication capacity and quality of thebase station. A relay station may be a fixed transceiver or a mobiletransceiver station depending on the specific conditions for deployingsuch as relation station. A subscriber station signal may hop throughone or more RSs before reaching a serving base station. The proposedIEEE 802.16j provides Mobile Multi-hop Relay (MMR) modes to use relaystations for enhanced coverage and service to subscribers. A multi-hoprelay wireless network under IEEE 802.16j can include MMR base stations(MMR-BSs) with the support of the MMR modes.

SUMMARY

In one aspect, a method for transmitting data control message streamsamong base stations, relay stations, and subscriber stations in awireless relay communication network is described to include operating abase station to receive protocol data units for subscriber stations fromnetworks; operating the base station to create relay protocol data unitsfrom the protocol data units based on relay station topology of one ormore relay stations under control of the base station; and operating thebase station to generate a transmission schedule with channel resourcesallocation information, in which at least one relay station isdesignated to receive corresponding relay protocol data units.

In another aspect, a method for receiving data and control messagestreams among base stations and relay stations in a wireless relaycommunication network is provided to include receiving relay protocoldata units; decoding the received relay protocol data units into one ormore of either or both of (1) subordinate relay protocol data units and(2) protocol data units; and transmitting the one or more subordinaterelay protocol data units and protocol data units to at least one of (1)one or more respective relay stations and (2) one or more subscriberstations.

In another aspect, a wireless relay communication network fortransmitting and receiving information among base stations, relaystations, and subscriber stations is described to include at least onebase station comprising a scheduler logic to determine a communicationpath from the base station to each subscriber station, and atransmitter/receiver component to transmit downlink data and controlmessages and to receive uplink data and control messages; and at leastone relay station comprising a scheduler logic to determine timeduration for transmitting and receiving information, and atransmitter/receiver component to transmit data and control messages andto receive data and control messages. The base station and relay stationoperate to communicate with at least one subscriber station.

In yet another aspect, a method for transmitting information among basestations, relay stations, and subscriber stations in a wireless relaycommunication network is provided to include using a frame structure toprovide a downlink relay allowing a relay station to transmit in partsof a downlink subframe of the frame structure.

These and other features are described in greater detail in the attacheddrawings, the detailed description and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an example of a multi-hop relay wireless network.

FIGS. 2 and 3 illustrate examples of communications in the network inFIG. 1.

FIGS. 4, 5A and 5B show three examples of relay frame structures.

FIG. 6 shows an example flow diagram of a base station scheduler.

FIG. 7 shows an example operation of a relay station in decodingreceived data and relaying data to one or more designated subordinaterelay stations and subscriber stations.

FIGS. 8, 9 and 10 illustrate three examples for providing radioresources in implementing relay frame structures described in thisapplication.

DETAILED DESCRIPTION

The Mobile Multi-hop Relay (MMR) modes to be defined in IEEE 802.16jneed to be backward compatible with the published IEEE 802.16-2004 andIEEE 802.16e-2005 standards. It is desirable that no changes be made toan existing mobile station (MS) in order to work with a relay station(RS) and a MMR base station (MMR-BS). Various types of relay stations,such as Fixed RS, Nomadic RS, and Mobile RS, and MMR-BSs are to bedefined in the IEEE 802.16j project Task Group (TGj). According to theIEEE 802.16j Project Authorization Request (PAR), this amendment is toenhance coverage, throughput and system capacity of 802.16 networks byspecifying 802.16 multihop relay capabilities and functionalities ofinteroperable relay stations and base stations.

The specification of this application describes, among others,implementations of systems and techniques for scheduling wirelesstransmission of data blocks between a base station (BS) and one or morerelay stations (RSs). The scheduling can be based on one or more factorssuch as the quality of the transmission links between the base stationand the relay stations, the amount of the data and the type of data forthe relay stations to support the subscriber stations (SS's) or mobilestations (MS's) in the relay station cell coverage areas. In one aspect,the scheduling can include assigning frequency blocks and time slots toeach of the relay stations for receiving or transmitting data blocks.The data blocks may include the trunk traffics for the relay station'scell and its subordinate cells if any.

In another aspect, a method for transmitting data streams between a basestation and relay stations is disclosed. The method includes receivingprotocol data units (PDU's) from a network for subscriber stations ormobile stations, encapsulating received PDU's to the same designatedrelay station, creating relay protocol data units (R-PDU's), andallocating pre-defined frequency blocks and pre-defined time slots forbase station's downlink transmission. A designated relay station can beconfigured to decode the downlink traffic according to known scheduleinformation. A transmission or reception schedule can include, in someimplementations, channel resources allocation information for a downlinkor uplink subframe.

In another aspect, the downlink schedule information is predefined andknown to relay stations in the wireless system. In this configuration, atransmission or reception schedule is not transmitted from the basestation to the one more relay stations.

In another aspect, downlink schedule information is produced by the basestation and transmitted in the downlink subframe. For example, thisschedule information can be included in a base station downlink MAP or arelay station specific downlink MAP, or a special downlink informationelement (IE).

In another aspect, downlink schedule information is produced by a relaystation and transmitted in the downlink subframe. For example, thisschedule information can be included in part of a general downlink MAPor a relay station specific downlink MAP, or a special downlinkinformation element (IE).

In another aspect, the downlink schedule information is produced by thebase station and transmitted in a different radio frequency channel fromthe radio frequency channel that is used to transmit the data packetsand is within the same frequency band. This radio frequency channel forcarrying the downlink schedule information can be a control channel witha narrow bandwidth. The downlink schedule information can also betransmitted in a different frequency band from a channel that carriesthe data packets. The downlink schedule information can be transmittedby using a different or the same technology for transmission of the datapackets and by using a different or the same frame structure fortransmission of the data packets. The downlink schedule information canbe transmitted by out-of-band transmission. This schedule information isreceived by relay station to perform reception or transmission in aparticular period of time or assigned time slots in a downlink subframe.

In another aspect, the downlink schedule information is produced by arelay station and transmitted in a different radio frequency channelfrom the channel for transmitting data packets to its subordinate relaystation. This channel for the downlink schedule information can be via acontrol channel. The downlink schedule information can be transmitted byusing a different or the same technology for transmission of the datapackets and by using a different or the same frame structure fortransmission of the data packets. The downlink schedule information canbe transmitted by out-of-band transmission. This schedule information isreceived by the subordinate relay station to perform reception ortransmission in a particular period of time or assigned time slots in adownlink subframe.

In another aspect, a method for receiving data streams at a relaystation from a base station is disclosed. The method includes receivinga special protocol data unit for a relay station, Relay Protocol DataUnit (R-PDU), decoding the R-PDU into its subordinate R-PDU's andregular PDU's, and transmitting them to the designated relay stationsand subscriber stations.

In another aspect, the uplink schedule information can be predefined andknown to relay stations in the wireless system and thus is nottransmitted.

In yet another aspect, the uplink schedule information is produced bythe base station and transmitted in a downlink subframe. For example,this schedule information can be included in a base station uplink MAPor a relay station specific uplink MAP, or a special uplink informationelement (IE).

In yet another aspect, the uplink schedule information is produced by arelay station and transmitted in a downlink subframe. For example, thisschedule information can be included in part of a uplink MAP or a relaystation specific uplink MAP, or a special uplink information element(IE).

In yet another aspect, the uplink schedule information is produced bythe base station and transmitted in a different radio frequency channelfrom the frequency channel that is used to transmit the data packets andis within the same frequency band. This radio frequency channel forcarrying the uplink schedule information can be a control channel with anarrow bandwidth. The uplink schedule information can also betransmitted in a different frequency band from a channel that carriesthe data packets. The uplink schedule information can be transmitted byusing a different or the same technology for transmission of the datapackets and by using a different or the same frame structure fortransmission of the data packets. The uplink schedule information can betransmitted by out-of-band transmission. This schedule information isreceived by relay station to perform reception or transmission in aparticular period of time or assigned time slots in an uplink subframe.

In yet another aspect, the uplink schedule information is produced by arelay station and transmitted in a different radio frequency channelfrom the frequency channel that is used to transmit the data packets andis within the same frequency band. This radio frequency channel forcarrying the uplink schedule information can be a control channel with anarrow bandwidth. The uplink schedule information can also betransmitted in a different frequency band from a channel that carriesthe data packets. The uplink schedule information can be transmitted byusing a different or the same technology for transmission of the datapackets and by using a different or the same frame structure fortransmission of the data packets. The uplink schedule information can betransmitted by out-of-band transmission. This schedule information isreceived by the subordinate relay station in order to perform receptionor transmission in a particular period of time or assigned time slots inan uplink subframe.

Other aspects of this application include implementations of techniquesfor transmitting downlink traffic streams via one or multiple relaystations, techniques for transmitting uplink traffic streams via one ormultiple relay stations, techniques for transmitting downlink and uplinksubframes with dedicated bursts allocation for relay stations, andtechniques for transmitting downlink and uplink subframes with dedicatedzones allocation for relay stations.

FIG. 1 illustrates a portion of an exemplary wireless multi-hop relaycommunication system that can implement a frame structure for relaystations described in this application. This system includes at leastone base station (BS) 100 and multiple relay stations 101 (RS1),102(RS2), and 103 (RS3) to provide radio coverage for serving one ormore subscriber stations (e.g., SS1 to SS8). The base station 100 can bea fixed base station and the relation stations 101, 102 and 103 can befixed relay stations, nomadic relay stations or mobile relay stations.Such a relay station can be located on a moving vehicle, a train, a shipor boat or other moving platforms. A relay station can be located insidea building, in an area with poor radio reception such as in a shadow ofa tall building or hill. As a specific example, two subscriber stationsSS3 and SS4 are shown to be in a coverage area of the RS1 101.

A relay station be used to extend a coverage of a base station or asuperordinate or parent relay station. Referring to the example in FIG.1, the relay stations RS1 101, RS2 102 and RS3 103 are subordinate tothe BS 100 because the BS 100 is connected to the network and is thegateway for the relay stations RS1 101, RS2 102 and RS3 103 to the restof the network. In this context, the BS 100 is the superordinate to therelay stations RS1 101, RS2 102 and RS3 103. In addition, it is possiblefor relay stations RS1 101, RS2 102 and RS3 103 under the control of thesuperordinate BS 100 to have superordinate and subordinate relationshipswith one another. For example, the relay station RS3 103 is subordinateto the relay station RS2 102 because RS3 103 communicates to BS 100through RS2 102. Hence, the relay station RS2 102 is superordinate tothe relay station RS3 103. In this context, BSs and relay stations inthe system in FIG. 1 can be classified into superordinate base stationsand subordinate base stations based on their relative relationships. TheBS 100 in FIG. 1 is the superordinate base station to all relay stationsand the relay station RS2 102 is a subordinate base station to the BS100 but a superordinate base station to the relay station RS3 103.

The base station 100 can include a scheduler logic to determine acommunication path from the base station 100 to each subscriber station,and a transmitter/receiver component to transmit downlink data andcontrol messages and to receive uplink data and control messages. Eachrelay station 101, 102 or 103 includes a scheduler logic to determinetime duration for transmitting and receiving information, and atransmitter/receiver component to transmit data and control messages andto receive data and control messages. The base station 100 and a relaystation operate to communicate with at least one subscriber station.

FIGS. 2 and 3 show example flow diagrams of downlink and uplink trafficstreams, including data and control signals, for the wireless multi-hoprelay communication system as illustrated in FIG. 1. Subscriber stationsSS1 and SS2 are directly served by the base station BS 100 withouthopping through any relay stations. The base station BS 100 communicateswith SS5 and SS6 via RS2 102 so that DL streams are first sent from BS100 to RS2 102 and then RS2 102 sends out DL streams for SS5 and SS6.For SS7 and SS8, the communications with BS 100 go through two hops viaRS2 102 and RS3 103.

FIG. 4 illustrates an example frame structure which includes downlinkand uplink subframes for the system in FIG. 1. The horizontal axisrepresents the time slot part of the radio resources and the verticalaxis represents the frequency part of the radio resources. The downlinkframe includes direct transmission from the base station BS 100 tosubscriber stations and transmission from the base station BS 100 tosubscriber stations via one or more relay stations. The uplink frameincludes direct transmission from subscriber stations to the basestation BS 100 and transmission from subscriber stations to the basestation BS 100 via one or more relay stations. The downlink frame andthe uplink frame are separated in time by a base stationtransmit-to-receive transition time (TTG). One frame may include onedownlink subframe and one or more uplink subframes. After completion ofthe one or more uplink subframes, a time gap known as the base stationreceiver/transmit transition gap (RTG) is added between the one uplinksubframe or the last uplink subframe and a downlink subframe of asubsequent frame.

In the frequency domain along the vertical axis in FIG. 4, differentchannel frequencies within a common frequency band or different channelfrequencies in different frequency bands are assigned to carry variousdata in the system in FIG. 1. This assignment of different channelfrequencies change within each subframe. In this example, the preambleof frame is first transmitted out by the BS 100 and is followed bytransmission of the frame control header (FCH), the downlink map(DL-MAP) and the uplink map (UL-MAP), which are allocated in the sametime lot for transmission at different channel frequencies in thisexample.

In the example in FIG. 4, the downlink subframe includes data burststransmitted from the base station 100 to its relay stations, data burststransmitted from one relay station to another relay station, and thedata bursts transmitted from relay stations to the associated subscriberstations. The downlink burst allocation can be provided by the DownlinkMap (DL-MAP) in IEEE 802.16 networks which describe a Medium AccessControl (MAC) message that defines burst start times for both timedivision multiplex (TDD) and time division multiple access (TDMA) by asubscriber station on the downlink. Other downlink messages differentfrom DL-MAP can also be used. In other implementations, the burstallocation signals can be provided by its parent base stations or relaystations. Similarly the uplink subframe can include the data bursts fromsubscriber stations to the designate relay stations, and the data burstsfrom the relay stations to the base station. The uplink burst allocationcan be provided by the Uplink Map (UL-MAP) or other uplink messages. Inother implementations, the burst allocation signals can be provided byits parent, superordinate base stations or superordinate relay stations.

The frequency-time allocations for the relay stations RS2 102 and RS3103 to receive and transmit data are highlighted and the related signaltransmission paths are indicated by arrowed lines. The TTG for the relaystation RS2 102 is illustrated and is set to meet the minimumTransmit-to-Receive Transition Time (TTG) for each relay station. A databurst from the BS 100 to a relay station is received by the relaystation. The receiving relay station decodes and removes part of thedata in the received data burst directed to the receiving relay stationand relays the rest of the received data burst to one or moresubordinate relay stations and one or more subordinate subscriberstations. The next subordinate relay station repeats a similar operationuntil proper data is routed to the intended subscriber stations in theserving area of the relay station and the base station. In the uplinksubframe, the reverse process is performed by the subscriber stations,the relay stations and the base station where protocol data units fromsubscriber stations are packaged by relay stations and are relayed tothe base station which sends the protocol data units from its subscriberstations to the network.

In the frame structure in FIG. 4, the entire frame has one singlepreamble, one UL-MAP, one DL-MAP and one FCH to provide the transmissionand receiving schedules for all relay stations and subscriber stations.The BS 100 transmits the preamble, the UL-MAP, the DL-MAP and the FCHfirst. In this frame design, two different relay stations may transmitdata bursts at the same time.

In another implementation, the time slots in the downlink subframe aredivided to different time zones and each time zone is designated for thebase station or one relay station to transmit data bursts only. FIGS. 5Aand 5B show two examples of this frame design.

FIG. 5A illustrates an example frame structure with divided transmissiontime zones for the downlink subframe for hoping through relay stations.In this example, the downlink subframe includes multiple downlinktransmission zones. In the DL BS Zone, data bursts are transmitted fromthe base station to its relay stations (RS1 and RS2) and subscriberstations (SS1 and SS2). The BS sends out the single UL-MAP, singleDL-MAP and single FCH for the entire frame. In the DL RS Zone1, the databursts are transmitted from relay station RS2 to the associated relaystations (RS3) and subscriber stations (SS5 and SS6). In the DL RS Zone2, the data bursts transmitted from relay station RS3 to the associatedsubscriber stations (SS7 and SS8). Following the first zone, e.g., theDL BS Zone, each zone may optionally start with a downlink midamblesymbol.

Similarly, an uplink subframe can also include multiple uplinktransmission zones (UL RS Zone 1, UL RS Zone 2 and UL BS Zone) in theframe in FIG. 5A. In the UL RS Zone 1, data bursts are transmitted fromthe subscriber stations (SS7 and SS8) to their relay stations (RS3), anddata bursts are transmitted from the subscriber stations (SS3 and SS4)to their relay stations (RS1). In the UL RS Zone2, some data bursts aretransmitted from relay station RS3 to the associated relay stations(RS2), and some data bursts are transmitted from relay station RS1 andother associated subscriber stations (SS1 and SS2) to base station. Inthe UL BS Zone, the data bursts are transmitted from relay stations (RS1and RS2) and other subscriber stations to base station. The relaystations RS1 and RS3 are in receiving mode in UL RS Zone1, thensubsequently some relays (RS1 and RS3) switch from receiving mode totransmitting mode. In UL BS Zone, all relay stations (RS1 and RS2) arein transmitting mode.

FIG. 5B illustrates another example frame structure with dividedtransmission time zones for the downlink subframe for hoping throughrelay stations. Different from the frame structure in FIG. 5A, the BSsends out its UL-MAP, DL-MAP and FCH at the beginning of its designatedDL BS Zone and each relay station also sends out its UL-MAP, DL-MAP andFCH at the beginning of its designated zone.

FIG. 6 shows an example flow diagram of a base station scheduler. Inthis example, a base station first groups the PDU's of a designatedrelay station to create a Relay Protocol Data Unit (R-PDU), thentransmits the schedule information and the R-PDU to the designated relaystation. As illustrated, the base station receives protocol data units(PDU's) directed to subscriber stations from the networks (Step 610).The base station groups received PDU's based on the designated relaystation (Step 620). This grouping is based on the relay station topologyin connection with the subordinate-superordinate relations with respectto the parent base station. The base station creates relay protocol dataunits (R1-PDU's) from the corresponding grouped PDU's (Step 630). Next,the base station creates multi-hop (N-Hop) relay protocol data units(Rn-PDU's) from subordinate RN-1-PDU's and the corresponding groupedPDU's (step 640). The base station then assigns channel resource, e.g.,time slots and frequency blocks, to the designated relay station withschedule information such as downlink relay MAP (step 650). The basestation transmits the schedule information such as downlink relay MAPand the respective RN-PDU's to the designated relay station (step 660).Referring to FIGS. 4, 5A and 5B, this transmission by the base stationis performed at the beginning of the downlink subframe.

FIG. 7 shows an example for a relay station to decode a R_(N)-PDU intoR_(N-1)-PDU's and PDU's, and then to transmit them to the designatedsubordinate relay stations and subscriber stations. This process is doneduring the downlink subframe. As illustrated, a relay station receives amulti-hop (N-Hop) relay protocol data unit (Rn-PDU) from its parent orsuperordinate base station (BS) or superordinate relay station (step710). The relay station decodes the received Rn-PDU into subordinateRn-1-PDU's and PDU's (step 720). Next in step 730, the relay stationtransmits Rn-1-PDU's and PDU's to the designated subordinate relaystations (RS's) and subscriber stations (SS′S).

In the above described relay frame structures, the radio resourceallocation can be implemented in various configurations. FIGS. 8, 9 and10 illustrate three examples.

FIG. 8 shows that a single RF channel is used to carry out theoperations in the frame structures in FIGS. 4, 5A and 5B. The givenbandwidth RF1 of the RF channel is divided into different frequencyblocks as shown in FIGS. 4, 5A and 5B. Two adjacent frames are shown.

FIG. 9 shows examples of how the schedule information is sent in thesame frequency band by using two different channels RF1 and RF2 in thesame frequency band. The schedule information can be sent together withthe allocated resources in the same radio frequency (RF) channel, asindicated by 802. The schedule information can also be sent in a RFchannel which is different from the RF channel of allocated resources,as indicated by 804. In this example, the second channel RF 2 is usedexclusively for providing allocated resources and the first channel RF1is used for both scheduling and providing allocated resources. Thedownlink schedule information can be transmitted by using a different orthe same technology for transmission of the data packets and by using adifferent or the same frame structure for transmission of the datapackets. This schedule information is received by relay station toperform reception or transmission in a particular period of time orassigned time slots in a downlink subframe.

FIG. 10 shows an example for using two different channels in twodifferent frequency bands for transmitting the schedule information anddata payload, respectively. The two channels RF1 and RF2 are in twodifferent frequency bands. The first channel RF1 is used as a controlchannel to provide scheduling information for the relay stations withoutbeing used to carry data payload. This channel RF1 can be a narrowbandchannel with a bandwidth less than that of the channel RF2. The controlchannel RF1 can be a wireless channel or a wired channel or wirednetwork connection which may be, e.g., Ethernet, and T1/E1 lines. Thesecond channel RF 2 is used to provide allocated resources for carryingdata payload. Therefore, the schedule information can be sent in adifferent RF channel or RF band, which is different from the RF channelof allocated resources, as indicated by 824, 826 and 828. The RF channelproviding the schedule information may not have the same bandwidth asthe RF channel providing the allocated resources, and they are notnecessary following the same frame structure.

The implementations can be used to allow for multi-hop relay wirelesscommunications among base stations, relay stations, and subscriberstations. Subscriber stations can include but are not limited to fixed,nomadic, and mobile stations. Relay stations can include but are notlimited to fixed, nomadic, and mobile relay stations. The describedtechniques may be implemented on a dedicated wireless infrastructure ormay be implemented as networks expansion on top of existing wirelesscommunications systems.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features specific to particularembodiments. Certain features that are described in this specificationin the context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Thus, particular embodiments have been described. Other embodiments arewithin the scope of the following claims.

1. A method for transmitting information among base stations, relaystations, and subscriber stations in a wireless relay communicationnetwork, comprising: using a frame structure to provide a downlink relayto transmit in parts of a downlink subframe of the frame structure,wherein the frame structure includes a base station zone comprising abase station downlink MAP at a beginning of the base station zone, thebase station zone for the base station to perform downlinktransmissions, followed by a relay station zone comprising a relaystation zone comprising a downlink MAP at a beginning of the relaystation zone, the relay station zone for the relay station to performdownlink transmissions.
 2. The method as in claim 1, comprising: usingthe frame structure to provide an uplink relay allowing a relay stationto transmit in parts of an uplink subframe within the frame structure.3. The method as in claim 1, comprising: configuring the frame structureto set a Receive-to-Transmit Transition Time (RTG) of each relay stationto meet a minimum time gap.
 4. The method as in claim 3, wherein theframe structure is applied to a downlink transmission only or an uplinktransmission only.
 5. The method as in claim 1, wherein the framestructure includes the relay station downlink MAP at a beginning of adesignated zone for the relay station.
 6. The method as in claim 1,wherein the frame structure includes the base station downlink MAP at abeginning of a designated downlink zone for the base station.
 7. Themethod as in claim 6, wherein the frame structure further includes aframe control header (FCH).
 8. The method as in claim 1, wherein theframe structure further includes a downlink midamble.
 9. The method asin claim 1, further including: operating a base station to communicatewith a subscriber station using the frame structure.
 10. The method asin claim 1, further including: operating the relay station tocommunicate with a subscriber station using the frame structure.
 11. Awireless relay communications system comprising a base station, adownlink superordinate relay station, a subordinate relay station and asubscriber station, wherein: the base station is configured to use aframe structure to provide a downlink relay to transmit in parts of adownlink subframe of the frame structure, wherein the frame structureincludes a base station zone comprising a base station downlink MAP at abeginning of the base station zone, the base station zone for the basestation to perform downlink transmissions, followed by a relay stationzone comprising a relay station zone comprising a downlink MAP at abeginning of the relay station zone, the relay station zone for therelay station to perform downlink transmissions.
 12. The wireless relaycommunications system as in claim 11, wherein the frame structure toprovide an uplink relay allowing a relay station to transmit in parts ofan uplink subframe within the frame structure.
 13. The wireless relaycommunications system as in claim 11, wherein the base stationconfigures the frame structure to set a Receive-to-Transmit TransitionTime (RTG) of each relay station to meet a minimum time gap.
 14. Thewireless relay communications system as in claim 13, wherein the framestructure is applied to a downlink transmission only or an uplinktransmission only.
 15. The wireless relay communications system as inclaim 11, wherein the frame structure includes the relay stationdownlink MAP at a beginning of a designated zone for the relay station.16. The wireless relay communications system as in claim 11, wherein theframe structure includes the base station downlink MAP at a beginning ofa designated downlink zone for the base station.
 17. The wireless relaycommunications system as in claim 16, wherein the frame structurefurther includes a frame control header (FCH).
 18. The wireless relaycommunications system as in claim 11, wherein the frame structurefurther includes a downlink midamble.
 19. The wireless relaycommunications system as in claim 11, wherein the base station isfurther configured to communicate with a subscriber station using theframe structure.
 20. The wireless relay communications system as inclaim 11, wherein the relay station is configured to communicate with asubscriber station using the frame structure.